The latest

The world’s two largest ice sheets lost an estimated 11.3 trillion metric tons from 1979 through 2023, adding about 31.4 millimeters to global mean sea level and increasing the exposure of coastal economies to flooding. The international assessment, published September 16 in Scientific Data, combined 42 independent estimates with observations from 27 satellite missions. It extended Greenland’s record to 1972 and Antarctica’s to 1979, showing that losses accelerated sharply from the 2000s and remained elevated through the 2010s.

Details

• Regional breakdown: Antarctica lost approximately 4.78 trillion tons between 1979 and 2023, while Greenland lost about 6.22 trillion tons from 1972 through 2023. Together, their meltwater amounted to roughly 3 quadrillion gallons, enough to lift global seas by more than an inch.
• Loss mechanism: About 84% of combined losses between 1979 and 2023 came from ice dynamics, as glaciers accelerated toward and into the ocean. The remaining 16% primarily reflected surface mass balance changes, including less snowfall and greater surface melting. Warmer oceans can erode shelves and glacier edges from below, weakening restraints on inland ice.
• Greenland shift: Greenland was relatively close to balance during the 1970s, before losses rose in later decades. During the 2010s, it lost an average of about 264 billion metric tons annually. Jakobshavn Glacier can retreat by approximately 50 meters a day.
• Antarctic concentration: West Antarctica was the dominant source of Antarctic mass loss, with annual ice discharge increasing substantially. Its glaciers are more exposed to ocean-driven instability because ice grounded below sea level can retreat through feedback processes. Heavy losses there have continued to shape the continent’s overall trajectory.
• Temporary slowdown: Relative stabilization between 2020 and 2023 did not reverse the longer-term trend. Unusually heavy East Antarctic snowfall temporarily offset major West Antarctic losses, while Greenland recorded fewer extreme summer melt events than in the previous decade. Lead author Inès Otosaka said subsequent observations indicate acceleration has resumed.
• Economic exposure: Even small increases in average sea level can expand the frequency and reach of coastal flooding. The implications are amplified by the concentration of population, infrastructure and economic activity along coastlines, while ice-sheet dynamics remain among the largest uncertainties in long-term sea-level projections.

Background

Earlier international assessments largely centered on satellite-era records beginning in the 1990s. By incorporating older observations from NASA and other missions, the assessment created a four-decade view in which multiple measurement techniques and independent studies converge on accelerating polar ice loss.

What’s next

The key indicators are annual ice discharge from West Antarctica and Greenland, alongside snowfall and surface melt. Observations after 2023 will show whether the renewed acceleration reported by Otosaka persists and how it changes sea-level projections.